Overexpression of the pectin lyase gene of Pseudomonas marginalis in Escherichia coli and purification of the active enzyme.

A pectin lyase gene (pnl) of Pseudomonas marginalis was cloned and overexpressed in Escherichia coli BL21(DE3). The pnl gene was amplified by PCR, inserted into pET29c with a six-His tag and the overproduced active enzyme was purified almost to homogeneity using a Ni(2+)-nitrilotriacetate-agarose column. The purified pectin lyase (PNL; EC 4.2.2.10, family 1) is inhibited by NAD+ (at concentrations above 0.25 mM), NADH or dithiothreitol. Evidence for the existence of a heat-labile protein inhibitor of PNL is also reported. The DNA-binding ability of PNL was demonstrated by DNA-retardation experiments. The partially purified enzyme was incubated with plasmid DNA and the complex was shifted to a higher molecular mass. Analysis of the electroeluted proteins from the protein-DNA complex revealed that one of the electroeluted protein bands was PNL. Antibodies against the overexpressed PNL were also prepared and partially purified.